mnrcaerobat

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I am planning a Smith Miniplane for my winter project. I have not started building the kit. This will be my fifth kit. I plan to use a four stroke. I have a Saito 72 that I could use on this plane. However, I am considering a Magnum 61 or OS 52. What do you think about powering this plane? Is anyone else building a mini this winter????

Maudib

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Hi mnrcaerobat,

I built one a couple years ago... I did a breif construction article... see it at:

http://www.renderwurx.com/rc/SmithMini/index.htm

I used the .46FX and it flew quite nicely... I think you are on target with a Saito .72... The Magnum .61 would fly it oto, but I think the O.S. .52 would leave you wanting.

Nice little plane... I still have the plans... and often thought I'd blow them up 100% and make a 50% scale one...

mnrcaerobat

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Nice review. I noticed you mentioned the cabanes. The plan calls for 0 degree incidence between the wings. The person I bought it from mentioned 0 degrees on the upper wing and the lower wing should be slightly positive 1 or 2 degrees to fly well. Another person mentioned the same thing in another forum from a Harry Higley Bipe book. How was yours done? Do you still fly the little bipe?

Maudib

My Feedback: (51)

It was my first real kit build... I had a blast and it turned out nice. IT flew quite well, but it had a tendency to balloon under power...

I tried increasing/decreasing the upper wing incidence a degree or two without success... Not sure what doing the bottom would do...

I do notice however that the stab is 0 degree as well... many of the more aerobatic bipes flew with a 1-2 degree positive incidence and this may very well fix the ballooning, but you're kind of committed either way you proceed...

I sold it a few months ago to make room in the hangar...

nchrome

Well I've had six of these little bypes and talk about a ball that is an understatment.On my laast two I had TT40s on then and they just flew just fine for me. On all the plaanes I had everything at 0 degrees and never r3ealy ballooned on me. Did loose upper wing on one and it didn't matter how much up I gave it it still came down. But it stil is a very fun plane to have and do it up any way you want it show us your covering talents. I do plan on getting one of these little butes back up in the air cause you don't have to disassemble them to transport it.

CafeenMan

Don't second-guess the plans. I've built two and am working on my third. 0-0 is the correct incidence for the Miniplane. If you have a ballooning problem and the wings are at 0 then it's most likely the engine thrust line that's off. These are great little planes. With a .60 it will be a lot of fun, but use throttle management.

Maudib

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You have built 3 of the most unique Smith Mini's out there being the only ones I have ever heard of that don't ballon on power... The plans call for zero engine thrust angle... basic design principle says there's gonna be some issues with that... but I also tried combinations of right and down...

I have spoken to several people about the Smith Mini... all with the same balooning problem. In fact I spoke to SIG and they told me themselves it was an inherent design personality.

bottom line is it isn't a big deal... in fact a mix could be setup to gradually add a little down elevator as the throttle increases... It's no problem to fly with as is anyway, just alittle more difficult to hold a nice level line in a high speed pass...

See below SIG's answer to an inquiry about this very "feature"...

_____________________________
Hello David,

The "ballooning" you refer to is normal for this, and every other, biplane I have flown. Biplanes, especially when they have a semi-symetrical or flat bottom airfoil are very speed sensitive, just like an R/C trainer. The faster you go, the more it wants to climb. And you have a pretty powerful engine in the OS 46FX. Much more than the old Enya 45 that was in the original. You can try some downthrust, but my experience is that it takes a LOT to even be noticable. My advice is to simply trim it out with a little down elevator and go fly.

I haven't flown a Smith Miniplane in a lot of years, but I distinctly remember that it really performed nice snap rolls.

Sincerely,
Mike Gretz
SIG Mfg. Co.
____________________________

CafeenMan

hmm.... maybe we are defining "ballooning" differently. I consider ballooning to be a sudden jump upwards under power. My miniplanes did climb under power, but that trimmed out with thrust adjustments.

Maudib

My Feedback: (51)

Looks like we are defining it differently...

Looking at plans from Dave Patrick, Miles Reed, Bob Godfrey and others, they all have positive incidence in the stab... and usually 0 in the wings... the right thrust suggested varies, but the down is usually 0 too...

At any rate... built as is, it's a fine plane... but it will most likely balloon under power...

mnrcaerobat

My Feedback: (197)

I think that I will build it to spec at 0 incidence all around. It sounds like per sig that the ballooning may be coming from the high performance 46 two stroke combined with the flat bottom wing. I found a Magnum 52 four stroke for $129 and I think I will buy it and use it for my engine. I just don't think that I need to overpower this little plane. CafeenMan, what have you used for motors in your previous two Smith's? What type of flying do you like?

CafeenMan

mnrcaerobat - My first was powered by a Fox .45 BB Schneurle (70's vintage). It was good power for the model and it balanced well. I sold it to a guy who put a .60 in it and hot-dogged it all over and eventually into a tree. That model was silked and doped and believe me I cried when he did that.

The next one I can't recall what was in it. My current model has a Fox .61 Eagle III. I don't know if I'll keep that engine in it though. It was brand new when I stuck it in the ground about 15 years ago and haven't run it since. I replaced the needle valve and put it on the stand. Seemed ok, but who knows.

I think a perfect engine for the mini would be the O.S. .52 or .72 4S. I think it will like the larger prop better than a high-rev 2S. Personally I like to fly large, smooth maneuvers. I'm not a throw it all over the sky kind of pilot. But my flying style shouldn't be taken into consideration because I'm not much of a pilot. I'm a way better builder than I'll ever be a pilot.

Best of luck with yours.

BTW.... it's a "flat bottom" wing, but the flat part isn't horizontal to the thrust line. That would actually be positive incidence. Make sure you measure to the center of the LE and TE to get it at 0.

bipeaddict

I powered my Smith with a RCV 60 4 stroke. Flys great. I put a servo in the tail the elevator. I put a servo to the rear of the cockpit for rudder pull-pull. I used Harry's book for construction/alignment tips.

I also put servos in the wings for the ailerons. Other modifications included a carbon fiber landing gear. I used JR DS368 servos in order to offset the increase in engine weight. It is covered in solartex.

Enjoy the build.

mnrcaerobat

My Feedback: (197)

do you have any pictures?

Norm Nestie

I Built a Smith Mini acouple a years ago, my first kit build. Followed plans exactly. When I took it out it's first year the torque roll to the left got me a couple of times and ended up having to rebuild the lower wing. NOW, I put 2 degrees of right thrust into the motor and with the OS 52 Surpass she takes off nice and level. It does baloon some on throttling up but I can live with that . Just a real pleasure to fly and is cute as hell.

mnrcaerobat

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Norm,

Do you find any other flying characteristics with the 2 degrees on the engine? Did it make the plane any slower? Does it still fly straight?

jayman618

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I had a enya 40 in mine and it was one of my favorite planes. Good Luck.

Jay Manion

jwl

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mnrcaerobat ,
The smith mini is my favorite "quick run to the field and fly" airplane.
I can fit it in the back seat of my 4 door sedan without any disassembly and nobody ever recognizes it as the smith mini.
Don't see many of the mini's around anymore. It's and older kit.
Yes, It definatley gains altitude during full throttle.
Can't do anything but trim it down.

I run the new Saito 56 in it and flies perfectly, but is not over powered.
I think the old OS fs 61 (4 strk) would be ideal.
A 72 4 stroke would be over kill.

Nothing like a serious flying plane.....no set up time, assembly or losing wing bolts.
Just take it out, fuel it up and flyit!

Jeff

Patriot

Smith mini was the first plane I built as a teenager, and can remember how I had to go home and build a trainer to learn how to fly. But once I was a better pilot and flew the miniplane quite a bit, I remember how the snap rolls were very impressive. It was a difficult plane to get on the ground at low power. It just kept wanting to fly.
Had a SuperTigre.40 in it, and flew it very well. I think your choice of a slighty larger four stroke will really give that little plane what it needs, as the one I built came out very tail heavy.

Patriot

P.S. Wish I stil had mine, but Dad sold it when I moved out years ago. Bummer.[]

CafeenMan

NEVER leave a plane behind!

Barnowl

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I built a Mini and have a Magnum 62 FS which is more than adequate power for this airplane. It is fun to fly and is really good looking. I strongly urge you to read Harry Higley's Bipes book before building, and that you modify the inter wing struts, which he specifically tells you how to do. I built mine according to the plans and the struts were a constant source of aggravation and bother (this may be and indication of my building skills), so I tore the wings open and rebuilt them as he reccommends. No more aggravation.

Patriot

Cafeenman, I wish I could have taken it, but no room when I went out to sea.[]

Maudib, that is a great idea. if you ever do blow up your plans, let me know. I would love to build an 88"ws Smith DSA-1. That would be beyond awesome, and very rare. I bet it would even fly much better than the original since it is much larger. Now you really got me thinking. hmmm..... How about a 45%, or even 50%? AW heck, lets just build a full scale that you can fly remotely or pilot?
YEAH BABY!!!!!!!!

Patriot

EscapeFlyer

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In my humble opinion, this is the best kit ever produced. You want to talk about fun!!! I powered mine with a saito .56. Definately not underpowered, and that was at an altitude of over 5,000 feet in Denver! The Saito.72 'ought to be rip roarin' fun!!!

I never ran into the ballooning problem- Everything was set at o%; the engine, wings, and elevator. In a knife edge it would pull towards the cockpit, so I added 1% of negative incidence in the top wing. It seemed to correct the problem without changing elevator trim much.

C.G. came out perfect with no other weight needed for balance using the .56.[8D]
This is a great plane!!!!!!

bretthan

I'm lookin at the smith mini too. Probly won't get it for a while, but the one question i have is are the wings removable. if they aren't it probly won't fit in the car.

nchrome

Bretthan man you musst have a really small car for this little bype not to fit in or even the trunk. Is your car RC also LOL. If your car is about average size you shouldn't have any problem halling it in the back seat or even the trunk. This plane is very portable and shoouldn't haave to be broken down. But if you have to yes it can be taken appart. But be careful of the upper wing cabaines cause they can move if not attatched to the wing.[:@]

Patriot

nchrome,

I sent you a PM.

Patriot